Update _getContributorsInformation & add fail

Update the _getContributorsInformation function to return the $.getJSON call which is basically the deferred being returned anyway.

Add a "graceful" fail statement that hides the spinner and add a message for the user.
dispatch languageAdded event from LanguageManager. Update all open documents for matching language.
Remove _getContributorsInformation
Include Text for contributors load fail.
Move $dlg and $contributors to higher scope
Render fail message with Mustache
add unit test for async call to defineLanguage while a document is open
Wrap fail text in .dialog-message
Merge pull request #3014 from TuckerWhitehouse/master

Fix About Dialog Contributors (Issue 3012 from Pull 2934)
fix jsdoc for CollectionUtils forEach
Merge pull request #3015 from adobe/jasonsanjose/issue-2962

Dispatch languageAdded event from LanguageManager